1. Field of the Invention
Novel modifications of 2-amino-4-(4-fluorobenzylamino)-1-ethoxycarbonylaminobenzene, and processes for their preparation
The invention relates to novel modifications of the compound 2-amino-4-(4-fluorobenzylamino)-1-ethoxycarbonylaminobenzene of the 
processes for their preparation and their use in pharmaceutical compositions.
2. Background Information
The compound of the formula I and its preparation is described in the patent DE 42 00 259.
This compound has, for example, anticonvulsive, antipyretic and analgesic activity and can thus be employed in pharmaceutical preparations.
In the crystallization of the compound of the formula I, however, in some cases very different mixed products are obtained with respect to the crystal size and form. Mixtures of crystal modifications are a great problem for pharmaceutical preparations. In particular, in the case of pharmaceutical forms having a high active compound content, physical inhomogeneties have a disadvantageous effect on adherence to constant pharmaceutical production conditions.
On the other hand, considerable variations in the stability, purity and uniformity of the finished product occur, so that the demands on the pharmaceutical quality of an active compound cannot be satisfied.
It is therefore of great interest to prepare the compound of the formula I in homogeneous crystalline form.
The invention is thus based on the object of preparing the compound of the formula I in homogeneous crystalline form which meets the pharmaceutical requirements.
It has now surprisingly been found that the compound of the formula I can be prepared in 3 different pure crystal modifications. Thus physically homogeneous compounds of the formula I can be prepared for the production of pharmaceutical finished products.
The 3 modifications, called A, B and C, have different physicochemical properties.
The in each case characteristic X-ray diffractograms are used for the identification of these three modifications of the compound of the formula I.
The modifications furthermore differ in their DSC curves (differential scanning calorimetry) and in some cases also in their IR spectra as well as by the crystal forms typical in each case.